Calculate access intervals between two objects.
Access <FromObjectPath> <ToObjectPath> [{AccessOptions}]
The Access Connect command can be used to calculate access intervals between objects and control the display of access graphics. An access interval is the time period during which line-of-sight visibility between two objects is possible while observing any constraints defined for either object.
Any number of the following {AccessOptions} can be included in the command:
| {AccessOptions} | Description |
|---|---|
| TimePeriod {Objects | {TimeInterval} | "<TimeIntervalList>"} | Enter the time period to use as the
access interval.
Specify Objects to use the object time periods as access intervals. If no TimePeriod option is entered this option is used. For valid {TimeInterval} values see Time Options. For valid "<TimeIntervalList>" specification see Component Specification. |
| MaxStepSize <Value> | The MaxStepSize limits the amount of
time that is allowed to elapse between sampling of the constraint
functions during access computations. The value is entered in
Connect time units and must be between 1.0e-5 and 315576000.0
seconds.
When this value is entered Step Size Control will be set to use a variable step to choose samples. |
| MinStepSize <Value> | The MinStepSize limits the amount of
time that is allowed to elapse between sampling of the constraint
functions during access computations. The value is entered in
Connect time units and must be between 1.0e-5 and 315576000.0
seconds.
When this value is entered Step Size Control will be set to use a variable step to choose samples. |
| ClockHost {1 | 2 | Base | Target} | Access reports the transmission/reception times using time values associated with the designated clockhost. A value of 1 or Base specifies the first object as the clock host; a value of 2 or Target specifies the second object as the clock host. |
| Mode {Transpond | Transmit | Receive} | The mode of signal transmission of the designated clock host, used in the apparent relative position computation used by Access. Transmit indicates that the clock host is transmitting; Receive indicates the clock host is receiving the signal. Both indicate that light time delay is considered. The value Transpond turns light time delay off (where distinctions between transmit and receive are no longer necessary). |
| AberrationType {Total | Annual | None} | Sets the model of aberration to be used in access computations. None indicates that aberration is ignored; Annual indicates that only annual aberration is accounted for; Total indicates that the full aberration correction is to be applied. |
| TimeConvergence <Value> | Sets the time tolerance used by the
access algorithms for determining the start and stop time of access
intervals. The event detection routine declares that an event is
found when either the value of the access constraint converges to
the desired value to within 8 digits or the time interval in which
the event lies is within the time tolerance. <Value> is
entered in Connect time units (1.0e-9 seconds <= t <= 1.0
seconds).
EventsBasedOnSamples must be set to Off for this value to have any effect. |
| LightTimeDelayConvergence <Value> | Sets the time tolerance used by the access algorithms for computing the light time delay between objects, when light time delay effects are considered. The light time delay is found whenever a correction to the previous estimate is within the time tolerance. <Value> is entered in Connect time units (1.0e-9 seconds <= t <= 0.1 seconds). |
| EventsBasedOnSamples {On | Off} | Turn EventsBasedOnSamples On to determine access intervals simply based on the samples without doing any extra sub-sampling. |
| AbsValueConvergence <Value> | Set the criterion used for convergence
for values near 0. <Value> must be between 1e-30 and 1e30
EventsBasedOnSamples must be set to Off for this value to have any effect. |
| RelValueConvergence <Value> | An event is said to be detected when a
constraint value's relative difference compared to the previous
sample is within this tolerance. <Value> must be between 0.0
and 1.0
EventsBasedOnSamples must be set to Off for this value to have any effect. |
| FixedSampleStep <Value> | Enter a step size value to control the
step size used in Access sampling. <Value> is entered in
Connect time units and must be between 1.0e-5 and 315576000.0
seconds.
When this value is entered Step Size Control will be set to use a fixed step to choose samples. |
| FixedStepTimeBound <Value> | Enter a value to have the fixed sample
steps calculated on a specific time boundary. <Value> is
entered in Connect time units and is between 0.0 and
86400.0seconds.
When this value is entered Step Size Control will be set to use a fixed step to choose samples. |
The graphics options available for this command in previous versions have been deprecated in STK 9. These options will be maintained for backward compatibility only. To set Access graphics options use the Graphics SetAccessGfx command. The deprecated options are:
[{InheritFlag}] [{LineGfxState} {AnimGfxState} {StaticGfxState}]
To calculate access over the scenario time period:
Access */Satellite/Sat1 */Facility/Fac1 TimePeriod UseScenarioInterval
To calculate access between 0.0 and 30000.0 epoch secs:
SetUnits / EpochSec
Access */Satellite/Sat1 */Facility/Fac2 TimePeriod "0.0" "30000.0"
To calculate the periods of access between the ERS1 satellite and the Baikonur facility in the stkDemo scenario:
Access */Satellite/ERS1 */Facility/Baikonur
To calculate access over the scenario time period, using a maximum step size of 240 seconds:
Access */Satellite/Sat1 */Facility/Fac1 TimePeriod Scenario MaxStepSize 240.0
To calculate access over the specified time period, also specifying the fixed sample step size, time bound value:
setunits * epochsec
Access */Satellite/Satellite1 Facility/Facility1 TimePeriod "0.0" "1200.0" EventsBasedOnSamples On FixedSampleStep 2.0 FixedStepTimeBound 60.0 Mode Transpond
To calculate the access over Facility1's Sunlight Interval List:
Access */Facility/Facility1 */Satellite/Satellite1 TimePeriod "Facility/Facility1 LightingIntervals.Sunlight Interval List"
Hint: This command returns a single message response. If no accesses can be determined, a "NoAccesses" message is returned.
Connect returns a message that includes the from object, the to object, the number of accesses and the start and stop time of all periods of access, as illustrated in the following example:/Application/STK/Scenario/stkDemo/Satellite/ERS1 /Application/STK/Scenario/stkDemo/Facility/Baikonur 3 1 Nov 2000 00:10:43.56 1 Nov 2000 00:21:46.46 1 Nov 2000 01:47:12.15 1 Nov 2000 02:02:05.32 1 Nov 2000 03:27:37.56 1 Nov 2000 03:41:17.87
This command belongs to the following group(s):
10
STK Programming Interface 11.0.1